Journal of Atmospheric Chemistry最新文献

The concentrations of suspended particulate matter PM10 in two-month winter period, i.e. December–January in years 2009–2015, were analyzed in relation to the values of wind speed in that time. It was possible to analyze results of air pollution measurements performed in the measuring station from the perspective of their higher levels in winter seasons (so-called smog episodes). Results from 3 stations of the Regional Inspectorate for Environmental Protection in Poznań (WIO? Poznań) served for better presentation of smog episodes in the region (black smog) and aimed at verification of correctness of the measurements of pollution immission in the monitoring station in Piotrkowice which is situated in vicinity of large combustion plant. The analysis confirmed that with low speeds of wind higher values of particulate matter PM10 were observed. The results of the analysis also show the displacement of pollutants according to the current wind direction or their local persistence for a longer time over one area.

The properties of the atmospheric aerosols depend on the source region and on the modifications that occur during their transport in the air. We have studied physical and chemical properties of aerosols along with their sink mechanism over two locations in southwest India, an urban site (Pune) and well-established climate observatory at Sinhagad (SINH), which represents rural and high altitude site. The ground-based measurements of aerosols, together with their radiative properties in this study have provided means to understand the observed variability and the impact on the aerosol radiative properties effectively over this region. The annual mean elemental carbon concentration (3.4 μg m^??3) at Pune was observed about three times higher compared to SINH (1.3 μg m^??3), indicating strong emissions of carbon-rich aerosols at the urban location. Aerosol optical properties were derived using the OPAC model which were used to compute the Aerosol radiative forcing (ARF) over both stations calculated using SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model shows pronounced seasonal variations due to changes in aerosol optical depth and single scattering albedo at both locations. The year-round ARF was 4–5 times higher over Pune (31.4?±?3.5 Wm^??2) compared to SINH (7.2?±?1.1 Wm^??2). The atmospheric heating rate due to aerosols shows a similar pattern as ARF for these locations. The heating was higher in the wintertime, ~?0.9–1.6 K day^??1 at Pune, and ~?0.3–0.6 K day^??1 at SINH. The estimated scavenging ratio was found high for NO₃^? and Ca.²⁺. The wet deposition fluxes of Cl^?, SO₄^2?, Na⁺, Mg²⁺ were observed higher for SINH as compared to Pune, due to the high amount of rain received at SINH.

The major ions in precipitation can reflect the conditions of the atmosphere, while stable isotopic characteristics provide information on the moisture source. In order to understand the local hydro-chemical features and regional geochemical cycle, it is essential to assess the chemical composition of precipitation and the associated sources. Therefore, a total of 57 precipitation samples (2016 to 2017) for major ions and 178 samples (2013 to 2017) for stable isotopes were collected from the Wengguo station and analyzed to explore the major ionic deposition and stable isotopic characteristics in the northern slopes of the Himalayas. The average pH and electrical conductivity were 6.82?±?0.45 and 15.36?±?11.67 μS cm^?1, respectively. Ca²⁺ followed by K⁺ and Mg²⁺ played a crucial role in neutralizing the precipitation acidity. The major ionic sources in the region were terrigenous (Ca²⁺, HCO₃^?, and Mg²⁺) and sea salt (Na⁺, Cl^?, and Mg²⁺), as well as anthropogenic emissions (SO₄^2? and NO₃^?) and biomass burning (K⁺). The total deposition flux of the major ions was higher in 2016 than in 2017 and was influenced by the higher precipitation. The average values of δ¹⁸O and δD in precipitation were???15.22?±?5.17 ‰ and???116.01?±?41.31 ‰, respectively. The precipitation stable isotopes were not significantly correlated to the local air temperature but the precipitation amount. Moreover, the variation in stable isotopes, local meteoric water line, and d-excess indicated the existence of continental and monsoon moisture transport systems. The transport of chemicals over the high elevation region from polluted cities in South Asia via moisture originating in the Bay of Bengal and the Arabian Sea was determined based on the source identification, clusters of air mass backward trajectory analysis, and the National Center for Environmental Prediction Final dataset. Thus, the ionic concentrations and stable isotopic characteristics of the precipitation from this study provided a valuable dataset to assess the atmospheric environment in the northern slopes of the Himalayas at Southern Tibetan Plateau.

Particulate matter (PM) can affect climate, air quality, human health, acid deposition and visibility, and contain a significant fraction of organic (OC) and elemental carbon (EC). Southern Africa is an important source region for OC and EC, however, little OC and EC data have been published for this region. This paper presents a multi-year, multi-site (an urban-industrial site in the Vaal Triangle, UI-VT; an industrially influenced site at Amerfoort, iI-AF; and two regional background sites at Skukuza and Louis Trichardt, RR-SK and RR-LT) PM with an aerodynamic diameter?≤?2.5?μm (PM_2.5) OC and EC dataset for South Africa. The median OC (9.3) and EC (3.2?μg.m^?3) concentrations at UI-VT were 1.3 to 2.5 and 2.7 to 4.4 times higher, if compared to the other sites. OC/EC ratios indicated that sources in close proximity to UI-VT were likely the main contributors, while sources that are more distant contributed fractionally more at the other sites. Household combustion for space heating and regional open biomass burning contributed to elevated levels during the cold and dry months at UI-VT. Regional open biomass burning also lead to higher OC and EC concentrations during the dry season at the industrially influenced site (iI-AF) and one of the regional background sites (RR-SK). From the seasonal concentration patterns, it seemed as if household combustion for space heating also contributed at these two sites during the cold months, but this could not be proven, even if only samples with limited influence of open biomass burning were considered. Such biomass burning influences were semi-quantified by considering MODIS fire pixels occurring within the air mass fetch region for each sample. For the remaining regional background site (RR-LT) the results suggesed that only regional open biomass burning contributed to elevated levels of OC and EC in the dry season and that household combustion for space heating did not contribute significantly.

The rapid economic development and significant expansion of urban agglomerations in China have resulted in issues associated with haze and photochemical smog. Central China, a transitional zone connecting the eastern coast and western interior, suffers from increasing atmospheric pollution. This study performed a spatio-temporal analysis of fine particulate matter (PM_2.5) pollution in Changsha, a provincial capital located in central China. Samples of PM_2.5 were collected at five different functional areas from September 2013 to August 2014. The PM_2.5 concentration at the five sampling sites was the highest in winter and the lowest in summer, with an average annual PM_2.5 concentration of 105.2?±?11.0?μg/m³. On average, residential sites had the highest concentrations of PM_2.5 while suburban sites had the lowest. We found that inorganic ionic species were dominant (~48%), organic species occupied approximately 25%, whereas EC (~3.7%) contributed insignificantly to the total PM_2.5 mass. Ion balance calculations show that the PM_2.5 samples at all sites were acidic, with increased acidity in spring and summer compared with autumn and winter. Air quality in Changsha is controlled by four major air masses: (1) Wuhan and the surrounding urban clusters, (2) the Changsha-Zhuzhou-Xiangtan urban agglomeration and the surrounding cities, and (3) southern and (4) eastern directions. The north–south transport channel is the most significant air mass trajectory in Changsha and has a significant impact on PM_2.5 pollution.

Real-time simultaneous measurements of rainwater and PM₁₀ chemistry were carried out at Delhi during the year 2016–17 in order to assess the levels of carbonaceous species and their wet scavenging during monsoon and non-monsoon seasons at Delhi. The PM₁₀ samples were collected Before Rain (BR), During Rain (DR) and After Rain (AR) events, while rainwater samples collected on an event basis. The ambient OC levels were always higher than the levels of EC during both monsoon and non-monsoon seasons in ambient aerosol as well as in rainwater. On an average, during rain (DR) 30% of OC aerosols and 28.2% of EC aerosols removed via wet scavenging process. In after rain (AR), 26.2% OC and 1.8% EC aerosols further decreased in comparison to DR samples due to the presence of OC and EC free air parcel. Overall it observed that the OC concentration significantly lowered from BR to DR and AR. However, EC concentrations in AR were found to be higher than DR samples indicating their build-up after the rains. The Scavenging Ratios (SRs) of OC and rain intensity had a significant positive correlation, whereas the SRs of EC showed a weak correlation with rain intensity. The SRs of EC were significantly higher during non-monsoon as compared to monsoon season. Such characteristics can be explained based on the particles size, source and the hygroscopicity of both types of carbonaceous aerosol.

Optical properties of atmospheric particles at Mexico City (UNAM) and Queretaro (JQRO) were measured with a Photoacoustic Extinctiometer (PAX) at 870?nm. The Mexico City Metropolitan Area has around 21 million inhabitants and Queretaro Metropolitan Area has little more than a million. Observations of meteorological parameters (relative humidity, solar radiation, and wind speed) were used to identify the rainy and dry seasons and explain the daily and seasonal behaviors of particles optical properties. The measurements were made from November 1, 2014 to July 31, 2016. At UNAM, the mean values of the scattering coefficient (B_scat) in cold dry, warm dry, and rainy seasons were 35.8, 27.1, and 31.3?Mm^?1, respectively; while at JQRO were 10.9, 11.9, and 15.0?Mm^?1. The average values of the absorption coefficient (B_abs) at UNAM during the cold dry, warm dry, and rainy seasons were 14.5, 12.7, and 12.7?Mm^?1, respectively; whereas at JQRO were 4.9, 4.7, and 3.9?Mm^?1. Both absorption and scattering coefficients showed similar diurnal behaviors, but at UNAM they are three times higher than JQRO. Concentrations of criteria gases (O₃, NO, NO₂ and NO_x) were also measured. At UNAM no difference was observed between the seasonal values for the single scattering albedo (SSA); while in JQRO, the rainy season had the highest seasonal value, being 13% higher than in the dry seasons. The Mass Scattering Cross-Section (MSC) values at UNAM were close to 2 m²/g; on the other hand, at JQRO the MSC values were lower than 1 m²/g. The results suggest a seasonal variability in the aerosol optical properties in both sites, which should be verified with more long-term studies.

Continuous online measurements of fine particulate matter mass (PM_2.5) and its chemical composition were carried out at an urban monitoring site in Wuhan from March 2017 to February 2018. The PM_2.5 mass concentration ranged from 6.3 to 223?μg/m³, with the highest in winter and the lowest in summer. Water soluble ions (WSIs) were the most abundant component in PM_2.5 (28.8?±?22.9?μg/m³), followed by carbonaceous aerosol (11.9?±?10.4?μg/m³) and elements (5.5?±?6.7?μg/m³). It is noteworthy that six episodes of sustained high PM were observed during the study period. Five major contributors of PM_2.5 were identified by positive matrix factorization (PMF) to be the iron and steel industry, fugitive dust, secondary photochemistry, traffic-related emission and biomass burning, contributing 26.3%, 5.5%, 29.5%, 29.2% and 9.6% to PM_2.5, respectively. Furthermore, conditional probability function (CPF), trajectory analysis and potential source contribution function (PSCF) were used to identify the influences of local activities and regional source. Local sources mainly include Wuhan iron and steel group, construction sites and urban trunk roads, etc. Three pollution transport pathways of PM_2.5 in Wuhan were identified to be northwest, east and south pathway, with the relative contribution of 40%, 17% and 43%, respectively. Western Henan, northern Shaanxi and southwestern Shanxi were identified to be the major potential source regions of PM_2.5 in Wuhan.

A total of 30 precipitation samples were collected at a remote site of Qinghai Lake in the northeastern Tibetan Plateau, China, from June to August 2010. All samples were analyzed for major cations (NH₄⁺, Na⁺, K⁺, Ca²⁺, and Mg²⁺) and anions (F^?, Cl^?, NO₃^?, and SO₄^2?), electric conductivity (EC), pH, dissolved organic carbon (DOC), and oxygen isotopic composition (δ¹⁸O). The volume-weighted mean (VWM) values of pH and EC in the precipitation samples were 7.2 and 19.0?μs?cm^?1. Ca²⁺ was the dominant cation in precipitation with a VWM of 116.9 μeq L^?1 (1.6–662.9 μeq L^?1), accounting for 45.7% of total ions in precipitation. SO₄^2? was the predominant anion with a VWM of 32.7 μeq L^?1, accounting for 47.1% of the total anions. The average precipitation DOC was 1.4?mg?L^?1, and it shows a roughly negative power function with the precipitation amount. The values of δ¹⁸O in the rainwater in Qinghai Lake varied from ?13.5‰ to ?3.9‰ with an average of ?8.1‰. The enrichment factor analysis indicates that crustal materials from continental dust were the major sources for Ca²⁺ in the precipitation samples. The high concentration of Ca²⁺ in the atmosphere played an important role in neutralizing the acidity of rainwater in Qinghai Lake area. Cluster analysis of air-mass trajectories indicates that the air masses associated with northeast and east had high values of NH₄⁺, SO₄^2?, and NO₃^?, whereas large Ca²⁺ loading was related to the air mass from west.

Lightning is an important source of nitrogen oxides (LNO_x). The actual global production of LNO_x is still largely uncertain. One of the reasons for this uncertainty is the limited available observation data. We measured the concentrations of total reactive nitrogen (NO_y), nitric oxide (NO) and nitrogen dioxides (NO₂) and then obtained NO_x oxidation products (NO_z: NO_z?=?NO_y - NO_x) at a station at the top of Mount Fuji (3776?m?a.s.l.) during the summer of 2017. Increases in NO_y and NO₂ were observed on 22 August 2017. These peaks were unaccompanied by increases in CO, which suggested that the observed air mass did not contain emissions from combustion. The backward trajectories of the above air mass indicated that it moved across areas where lightning occurred. The NO_y concentration was also calculated by using a chemical transport model, which did not take NO_x produced by lightning into account. Therefore, the NO_y concentration due to lightning can be inferred by subtracting the calculated NO_y from the observed NO_y concentrations. The concentration of NO_y at 13:00 on 22 August 2017 originating from lightning was estimated to be 1.11?±?0.02 ppbv, which comprised 97?±?2% of the total NO_y concentration. The fractions of NO₂ and NO_z in the total NO_y were 0.54?±?0.01 and 0.46?±?0.03, respectively. The NO concentration was below the detection limit. We firstly observed increase of concentrations of NO_y originating from lightning by ground-based observation and demonstrated the quantitative estimates of LNO_x using model-based calculation.